design is built around the Teensy4.1 processor (available on Amazon, PJRC, etc.) It has 8MB of flash, runs at 600MHz, and has a fast double precision capable floating point unit. The T4.1 is the fastest/most capable OnStep supported MCU. This has a moderate amount of soldering necessary but most components needed to build one of these can be obtained from EasyEDA/LCSC and eBay. **Note: This design is for non-commercial use only (see License terms, CC-BY-NC-SA 3.0)** **Note: OnStepX has untested support for this board** This controller includes the following features: * Power: Coaxial power jack, fuse, and power switch connection. * Stepper drivers: Four, one for RA/Azm, one for Dec/Alt, one for a focuser, and one for a rotator/second focuser. It's designed to support full control (microstep mode etc.) of older StepStick drivers as well as TMC SPI ones, in all four sockets. All stepper motor connections are available on RJ jacks at the PCB back (screw terminals are optional.) * Needs a DS3231 RTC Module with AT24C32 4KB EEPROM to function (eBay etc.) * WiFi or Ethernet: WeMos D1 Mini ESP8266 foot-print (uses Serial2.) * Micro USB port built into the Teensy4.1. * Mini speaker for alert buzzer. * DB15 15 pin D-Sub connector: primary external I/O for Gnd, +3.3V, 5V, two Home Switches, PEC, PPS, I2C, the Serial1 port, and two channels of A/B encoder inputs. * 3.5mm stereo mini jack: secondary external I/O for Limit Switches and Reticle. * RJ12 Modular connector: ST4 guider interface (with optional 5V power.) History - Version3.6 - First release - Version3.61 - Added blocking diode to WeMos D1 Mini socket, moved serial RX/TX to swapped pins D7/D8